ObjectiveThis cross-sectional study was conducted to estimate the prevalence of somatic and psychological complaints (SPCs) and to investigate the association of SPCs with insomnia in a sample of the general adult population of Japan.MethodsWe randomly selected 4000 adult residents (≥20 years old) from five areas of Japan using stratified sampling and conducted interviews using a structured questionnaire. The questionnaire solicited information about eight somatic symptoms, eight psychological symptoms, three sleep problems, and demographic and health-related information. A total of 3030 subjects completed questionnaires, giving a response rate of 75.8%.ResultsStiff neck/shoulder (45.3%), backache (35.1%), and fatigue (31.4%) were the most common complaints in this population. In general, SPCs were more prevalent in younger persons and in women. Logistic regression analyses, controlling for other factors, showed that insomnia was significantly associated with a number of SPCs: backache (odds ratio [OR] = 1.4, 95% confidence interval [CI] = 1.1–1.6), epigastric discomfort (OR = 1.7, 95% CI = 1.3–2.2), weight loss (OR = 2.0, 95% CI = 1.2–3.3), headache (OR = 1.7, 95% CI = 1.3–2.2), fatigue (OR = 1.7, 95% CI = 1.4–2.1), worrying (OR = 1.6, 95% CI = 1.1–2.3), irritability (OR = 1.4, 95% CI = 1.1–1.7), and loss of interest (OR = 1.8, 95% CI = 1.2–2.7).ConclusionsSPCs were common and were largely associated with insomnia in the general adult population of Japan. Further study is needed to examine the causal links between SPCs and insomnia.